Forwarding table management

ABSTRACT

Disclosed herein are system, method, and computer program product embodiments for representing a forwarding information base (FIB) in a database. An embodiment operates by determining that a first routing prefix of a first forwarding entry in the FIB is a less specific routing prefix than a second routing prefix in a second forwarding entry in the FIB. The embodiment determines that a first next hop of the first routing prefix is equal to a second next hop of the second routing prefix. The embodiment removes the second forwarding entry from the FIB. The embodiment then inserts the first forwarding entry into a database (e.g., a longest exact match (LEM) database or a longest prefix match (LPM) database) based on a prefix length of the first routing prefix of the first forwarding entry.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of provisional U.S. PatentApplication No. 62/593,834, titled “Forwarding Table Management For TheInternet” and filed on Dec. 1, 2017, which is incorporated herein byreference in its entirety.

BACKGROUND

Routers route packets across the Internet using a routing table. Arouting table (or routing information base (RIB)) can include optimalpaths toward individual routing prefixes. A router can insert a routeinto the RIB whenever the router learns of the new route. But, routersdo not use the RIB to forward packets; rather, a forwarding informationbase (FIB) is used to forward packets.

A FIB can be a database that includes forwarding entries representing anoutgoing interface and next hop information for each reachabledestination routing prefix. If not all the forwarding entries can bestored in the FIB, then the router may drop traffic to destinations notprogrammed in the FIB.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated herein and form a part of thespecification.

FIG. 1 is a block diagram of a router configured to represent aforwarding information base (FIB) that includes routing prefixes for anetwork in one or more databases, according to some embodiments.

FIG. 2 is a block diagram illustrating an example FIB of a router,according to some embodiments.

FIG. 3 is a block diagram illustrating an example FIB of a routerorganized using a trie data structure to enable compression of the FIB,according to some embodiments.

FIG. 4 is a flowchart illustrating a process for representing a FIB thatincludes routing prefixes for a network in one or more databases,according to some embodiments.

FIG. 5 is an example computer system for implementing variousembodiments.

In the drawings, like reference numbers generally indicate identical orsimilar elements. Additionally, generally, the left-most digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

DETAILED DESCRIPTION

Provided herein are system, apparatus, device, method and/or computerprogram product embodiments, and/or combinations and sub-combinationsthereof, for representing a forwarding information base (FIB) thatincludes routing prefixes for a network (e.g., the Internet) in one ormore databases (e.g., a database implemented using associative memory).

Routers are often unable to store a FIB that includes all routingprefixes for a network (e.g., the Internet) in specialized hardware,such as on-chip temary content-addressable memory (TCAM). These storageconstraints can result in the routers' inability to forward a packetwithin the network. Embodiments herein solve this technological problemby compressing the FIB and then separating the routing prefixes in thecompressed FIB into two different databases used to forward packets.

FIG. 1 is a block diagram of a router 102 configured to represent a FIBthat includes the routing prefixes for a network (e.g., the Internet) inone or more databases, according to some embodiments. Router 102 caninclude router information base (RIB) 104, FIB 106, longest prefix match(LPM) database 108, and longest exact match (LEM) database 110.

RIB 104 can be a routing table. For example, RIB 104 can include theentire Internet routing table. RIB 104 can also include the best pathstoward individual routing prefixes. A routing prefix can represent asubnetwork, which can be a logical subdivision of the network.

In some embodiments, a routing prefix can be an Internet Protocol (IP)routing prefix. The IP routing prefix can summarize IP addresses thatshare some common bits at the beginning of their addresses. The IProuting prefix can be expressed in a Classless Inter-Domain Routing(CIDR) notation. In the CIDR notation, the routing prefix can be writtenas the first address of a network, followed by a slash character (/),and ending with the bit-length of the prefix. For example,198.51.100.0/24 is an IP routing prefix of an IP version 4 networkstarting at the given address, having 24 bits allocated for the routingor network prefix, and having 8 bits reserved for host addressing.Though the routing prefix is described in terms of an IP routing prefixbelow, based on the description herein, the routing prefix can beassociated with other types of routable network protocols.

RIB 104 can store routing information for the Internet, according tosome embodiments. Router 102 can add or delete routes from RIB 104 inresponse to routing updates. For example, router 102 can insert a routeinto RIB 104 that is learned via a dynamic routing protocol (e.g.,Border Gateway Protocol (BGP)). Router 102 can insert a static routeinto RIB 104. Router 102 can also store directly attached networks inRIB 104.

Router 102 can store multiple available routes for each routing prefixin RIB 104. Router 102 can indicate which one or more routes of theavailable routes is the best route for each routing prefix. Router 102can continually recalculate the best route for each routing prefix inresponse to routing updates.

Router 102 can use the routing information in RIB 104 to route a packetto a particular destination. Router 102 can route a packet to aparticular destination based on hop-by-hop routing. In hop-by-hoprouting. RIB 104 can include, for each reachable destination (or routingprefix), the network address of the next router along the path to thedestination. This network address can be referred to as a “next hop.” Inother words, RIB 104 can include routing prefix/next hop associations.

These associations can tell router 102 that a particular destination canbe optimally reached by sending a packet to a specific router thatrepresents the “next hop” on the way to the final destination. The nexthop association can also indicate the outgoing interface to use to sendthe packet to the final destination.

Router 102 can use RIB 104 to forward a packet along a path to the finaldestination. But this is may be slow for some routing applications. Toforward the packet, router 102 performs a lookup operation in RIB 104,which can be slow because some associations in RIB 104 can include nexthops that are not directly connected to router 102. As a result, router102 can perform a recursive lookup to find the next hop—this iterativeprocess is often slow. To solve this technological problem, router 102can use FIB 106 to forward packets.

In some embodiments, FIB 106 is a forwarding table that router 102 canuse to forward packets to their next hops on the way to their finaldestinations. FIB 106 can include a subset of the information in RIB104. RIB 104 can be optimized for efficient updating by routingprotocols (e.g., BGP) and other control plane methods, whereas FIB 106can be optimized for fast lookup of destination addresses.

FIB 106 can include a set of forwarding entries, according to someembodiments. Each forwarding entry can map a reachable routing prefix tonext hop information. The next hop information can include the networkaddress of the next hop and the outgoing interface to send the packet.

Router 102 can use FIB 106 to forward each individual packet thattraverses the router, according to some embodiments. Router 102 canselect the best matching forwarding entry for each individual packet.For example, router 102 can select the forwarding entry with the longestrouting prefix that matches the destination address in the packet.

Router 102 can maintain a mirror image of the routing informationincluded in RIB 104 in FIB 106. In some embodiments, router 102 candetermine a next hop for a routing prefix stored in RIB 104. Router 102can receive the routing prefix via advertisement from another router(e.g., one of routers 208, 210, 212, and 214 in FIG. 2) using a routingprotocol (e.g., BGP). Router 102 can then store a forwarding entry inFIB 106 representing a mapping from the routing prefix to the next hop.

In some embodiments, when routes are copied from RIB 104 to FIB 106,their next hops can be resolved, outgoing interfaces can be computed,and multiple forwarding entries can be created when the next hopresolution results in multiple paths to the same destination. As aresult, router 102 can use the resulting forwarding entries in FIB 106to forward packets and thereby avoid potentially slow recursive lookupsin RIB 104 to find the next hop.

If not all the forwarding entries can be stored in FIB 106, router 102may drop packets to destinations not programmed in FIB 106. But thenumber of routing prefixes for the network (e.g., the Internet) can bevery large. As a result, router 102 can require a large amount of memoryto store the routing prefixes for the network. To solve thistechnological problem, router 102 can store FIB 106 in main memory(e.g., random access memory (RAM)). Main memory can be inexpensive andhave storage capacity for the network's routing prefixes. But, router102 may not be able to perform fast lookups when FIB 106 is stored inmain memory that includes a large number of routing prefixes (e.g., forthe Internet). In this scenario, router 102 may drop packets todestinations not programmed in FIB 106.

In some embodiments, routers address this issue by storing the FIB inspecialized hardware that provides improved lookup times. For example,routers can store the FIB in ternary content-addressable memory (TCAM).But, for some applications, storing the FIB in hardware can beexpensive. In addition, the hardware may have storage capacityconstraints and thus unable to store the routing prefixes for thenetwork (e.g., the Internet). Due to the storage constraints, the routermay need to select a subset of routing prefixes to store in the FIB. Thesubset of routing prefixes may exclude the best path to forward apacket, thus resulting in inefficient packet forwarding.

In some embodiments, these technological problems are solved bycompressing FIB 106 and then separating the forwarding entries in thecompressed FIB 106 into two different databases: LPM database 108 andLEM database 110. Router 102 can first attempt to use LEM database 110to forward packets based on longest exact match to routing prefixes oflength /24 and /32. This can be more efficient because router 102 oftenforwards packets to routing prefixes of length /24 or /32. Router 102can forward packets based on longest exact match to routing prefixes ofother lengths that are greater than or less than length /24 or /32(e.g., routing prefix lengths of /2, /4/, /8, /16, /48, /96, etc.). Ifthere is no match in LEM database 110, router 102 can use LPM database108 to forward packets based on longest prefix match. This can enablerouter 102 to forward packets that do not match forwarding entries inLEM database 110 at the expense of longer lookup times. Because the FIB106 is compressed before programming the forwarding entries into LPMdatabase 108 and LEM database 110, the entire routing table (e.g., theentire Internet routing table) can be represented across LPM database108 and LEM database 110. Thus, router 102 can program forwardingentries into LPM database 108 and/or LEM database 110 based on thecompressed FIB 106.

In some embodiments, LPM database 108 can be a hardware implementeddatabase. Router 102 can store a portion of the compressed FIB 106 intoLPM database 108. Router 102 can store forwarding entries with routingprefixes having different prefix lengths than /24 and /32 into LPMdatabase 108. Router 102 can store forwarding entries with routingprefixes having different prefix lengths (e.g., different than routingprefix lengths of /2, /4, /8, /16, /48, /96, etc.) into LPM database108. Router 102 can store the forwarding entries starting with theforwarding entries having routing prefixes of shortest length untilthere is no more space in LPM database 108.

In some embodiments, LEM database 110 can be a hardware implementeddatabase. LEM database 110 can be an exact match database. Router 102can store the portion of the compressed FIB 106 that is not stored inLPM database 108 in LEM database 110. In other words, router 102 canstore forwarding entries with routing prefixes equal to /24 and /32 intoLEM database 110. Router 102 can store forwarding entries with routingprefixes equal to other lengths (e.g., equal to routing prefix lengthsof /2, /4, /8, /16, /48, /96, etc.) into LEM database 110. Thecombination of LPM database 108 and LEM database 110 can store theentire Internet routing table represented in compressed FIB 106,according to some embodiments.

In some embodiments, router 102 can forward a packet based on theinformation in LPM database 108 and LEM database 110. Router 102 canfirst check LEM database 110 for the next hop for a packet. If router102 does not find the next hop in LEM database 110, router 102 can checkLPM database 108 for the next hop for the packet. If router 102 does notfind the next hop in LPM database 108, router 102 can drop the packet.

FIG. 2 is a block diagram illustrating an example FIB 106 of router 102of FIG. 1, according to some embodiments. FIG. 2 is discussed withreference to FIG. 1. In FIG. 2, router 102 can route a packet 202according to information in FIB 106. FIB 106 can include forwardingentries including routing prefixes advertised from routers 208, 210,212, and 214. Routers 208, 210, 212, and 214 can represent BGPneighbors.

Router 208 can advertise routing prefixes 231 and 232. Router 210 canadvertise routing prefixes 233, 234, and 235. Router 212 can advertiserouting prefixes 236 and 237. Router 214 can advertise routing prefix238.

In some embodiments, router 102 can cause FIB 106 to map each advertisedrouting prefix to a next hop in next hops 228. Each mapping can berepresented as a forwarding entry in FIB 106. For example, in FIG. 2,FIB 106 can include forwarding entries 220-227. For example, forwardingentry 220 can map routing prefix 23.23.0.0/16 to next hop nh1(represented as next hop 229).

In some embodiments, a next hop in next hops 228 can include a mappingof an outgoing interface of router 102 to a next hop address. The nexthop address can represent the next router (or destination) to whichpacket 202 is to be sent on the way to its final destination. Theoutgoing interface can represent the outgoing interface for sendingpacket 202 to the next router. For example, next hop 230 maps outgoinginterface e 3/1 to next hop address 20.20.20.1

In FIG. 2, FIB 106 can map route 233 to next hop 229. This can berepresented as forwarding entry 220. FIB 106 can map route 236 to nexthop 230. This can be represented as forwarding entry 221. FIB 106 canmap route 231 to next hop 229. This can be represented as forwardingentry 222. FIB 106 can map route 234 to next hop 229.

This can be represented as forwarding entry 223. FIB 106 can map route235 to next hop 229. This can be represented as forwarding entry 224.FIB 106 can map route 237 to next hop 230. This can be represented asforwarding entry 225. FIB 106 can map route 238 to next hop 230. Thiscan be represented as forwarding entry 226. FIB 106 can map route 232 tonext hop 230. This can be represented as forwarding entry 227.

In some embodiments, a next hop can include one or more mappings of anoutgoing interface to a next hop address. For example, in FIG. 2, nexthop 229 can map outgoing interface e1/1 of router 102 to next hopaddress 10.10.10.1 of router 204, and outgoing interface e3/1 of router102 to next hop address 20.20.20.1 of router 206.

In FIG. 2, router 102 can use the destination address of packet 202 todetermine which address should next receive packet 202. As discussedabove, this can be referred to as the next hop address. For example,router 102 can select a forwarding entry in FIB 106 that includes aroute prefix that represents the longest prefix matching the destinationaddress of packet 202. Router 102 can then route packet 202 to itsdestination by sending packet 202 to the next hop corresponding to theselected forwarding entry. Router 102 can send packet 202 to an outgoinginterface for the next hop corresponding to the selected forwardingentry in FIB 106.

For example, in FIG. 2, router 102 can select forwarding entry 221 inFIB 106 for packet 202. Router 102 can then send packet 202 to next hopnh2 (represented as next hop 230 in next hops 228). In other words,router 102 can send packet 202 out outgoing interface e3/1 to next hopaddress 20.20.20.1 of router 206.

In another example, in FIG. 2, router 102 can select forwarding entry220 in FIB 106 for packet 202. Router 102 can then send packet 202 tonext hop nh1 (represented as next hop 229 in next hops 228). In otherwords, router 102 can send packet 202 out outgoing interface e1/1 tonext hop address 10.10.10.1 of router 204, or out outgoing interfacee3/1 to next hop address 20.20.20.1 of router 206.

As discussed, the number of routing prefixes for the network (e.g., theInternet) can be large. For example, if router 102 is used on theInternet, it can require a large amount of memory to store the routingprefixes in FIB 106. In some embodiments, router 102 can solve thistechnological problem by compressing FIB 106 to enable therepresentation of the entire routing table in hardware (e.g., in LPMdatabase 108 and/or LEM database 110). Router 102 can compress FIB 106based on the observation that many of the forwarding entries in FIB 106(e.g., mappings 220-227) do not need to be stored. This is because manyof the forwarding entries are redundant.

In some embodiments, router 102 can compress FIB 106 by representing twoforwarding entries in FIB 106 using a single forwarding entry. Forexample, if FIB 106 includes a forwarding entry with a general routingprefix and a forwarding entry with a more specific routing prefix of thegeneral routing prefix, and both routing prefixes are mapped to the samenext hop, FIB 106 can avoid storing the forwarding entry for the morespecific routing prefix. This is because if packet 202 matches the morespecific routing prefix, it will also match the general routing prefix.Moreover, because both routing prefixes are mapped to the same next hop,the general routing prefix is sufficient by itself to enable router 102to forward packet 202 to the next hop. Thus, router 102 can representthe two routing prefixes having the same next-hop information using justa single forwarding entry including the more general routing prefix. Inother words, router 102 can keep a forwarding entry with the smallestlength routing prefix common among a set of forwarding entries in FIB106 that point to the same next hop.

For example, in FIG. 2, FIB 106 can store forwarding entries 220 and222. But forwarding entry 222 is redundant. This is because if router102 matches packet 202 to forwarding entry 222, router 102 can alsomatch packet 202 to forwarding entry 220. Because both forwardingentries 220 and 222 go to the same next hop 229, router 102 can use thegeneral forwarding entry 220 in place of the more specific forwardingentry 222. Thus, router 102 can remove forwarding entry 222 from FIB 106to save memory space.

In another example, in FIG. 2, if packet 202 matches forwarding entry224, it can also match forwarding entry 223 and go to the same next hop229. Thus, router 102 can remove forwarding entry 224 from FIB 106 tosave memory space. In another example, if packet 202 matches forwardingentry 226, it can also match forwarding entry 225 and go to the samenext hop 230. Thus, router 102 can remove forwarding entry 226 from FIB106 to save memory space.

FIG. 3 is a block diagram illustrating an example of FIB 106 of router102 organized using a trie data structure to enable compression of FIB106, according to some embodiments. FIG. 3 is discussed with referenceto FIGS. 1 and 2. In FIG. 3, router 102 can organize forwarding entriesin FIB 106 using trie data structure 300. A trie data structure can be atype search tree.

In FIG. 3, trie data structure 300 can have one or more levels. The topof trie data structure 300 can be a default route (e.g., routing prefix/0). This can be represented as level 301. The top route of trie datastructure 300 can have the shortest routing prefix length.

The next level of trie data structure 300 can be level 302. The routingprefixes in level 302 can be children of the top route in level 301. Inother words, the top route of trie data structure 300 can be a moregeneral routing prefix that includes the routing prefixes in level 302.For example, one or more routing prefixes in level 302 can have thedefault routing prefix in level 301 as their parent.

The next level of trie data structure 300 can be level 303. The routingprefixes in level 303 can be children of a routing prefix in level 302.In other words, a routing prefix of trie data structure 300 at level 302can be a more general routing prefix that includes the routing prefixesin level 303. For example, one or more routing prefixes in level 303 canhave a routing prefix of trie data structure 300 at level 302 as theirparent.

In some embodiments, router 102 can organize FIB 106 using trie datastructure 300 to enable the compression of FIB 106 based on redundancyin the forwarding entries in FIB 106 (e.g., forwarding entries 220-227in FIG. 2). For example, organizing FIB 106 using trie data structure300 can enable compression by enabling router 102 to identify in FIB 106a general routing prefix and a more specific routing prefix of thatgeneral routing prefix which are both mapped to the same next hop.Router 102 can mark the more specific routing prefix for compression.

For example, in FIG. 3, route 304 can represent routing prefix at level302. Route 304 can have the default routing prefix (e.g., 0.0.0.0/0) asits parent. Route 305 can represent a routing prefix at level 303. Route305 can have a level 302 routing prefix as its parent. In this case,route 305 can have route 304 as its parent. In other words, route 304can be a general routing prefix and route 305 can be a more specificrouting prefix of that general routing prefix. To compress FIB 106,router 102 can determine if route 304 and route 305 both have the samenext hop. If they do, router 102 can mark route 305 for compression.

In some embodiments, router 102 can compress FIB 106 in response to aroute being copied from RIB 104 to FIB 106. For example, router 102 canadd a forwarding entry corresponding to a level L routing prefix R toFIB 106. Router 102 can compare the next hop of routing prefix R withthe parent routing prefix of R (e.g., level L−1 route prefix R_(p)). Ifrouter 102 determines that both routing prefix R and routing prefixR_(p) have the same next hop, router 102 can mark the forwarding entrycorresponding to routing prefix R for compression. Router 102 can thenrepeat the same compression process on all children routing prefixes atlevel L+1 (e.g., R_(c1) to R_(cn)). Router 102 can mark forwardingentries corresponding to the children routing prefixes for compressiondepending on whether their next hops are the same as the newly insertedrouting prefix R.

Router 102 can reduce the size of FIB 106 using this compressionprocess. For example, in some cases, the above compression process cancompress FIB 106 down to 40% of its original size (e.g., from 655 Kforwarding entries to 255 K forwarding entries).

In some embodiments, when router 102 marks a forwarding entrycorresponding to a routing prefix for compression, router 102 can removethe forwarding entry from FIB 106. In some other embodiments, whenrouter 102 marks a forwarding entry for compression, router 102 canavoid inserting the forwarding entry into either LPM database 108 or LEMdatabase 110.

In some embodiments, router 102 can generate a hardware instruction foreither LPM database 108 or LEM database 110. This hardware instructioncan program LPM database 108 or LEM database 110 to store a forwardingentry in FIB 106.

In some embodiments, router 102 can reduce the size of FIB 106 usingthis compression process. But even after compressing FIB 106, FIB 106may still be too large to store in a database. For example, FIB 106 maystill be too large to store in a database implemented using associativememory. To overcome this technological problem, in some embodiments,router 102 can separate the forwarding entries in the compressed FIB 106into two databases: LPM database 108 and LEM database 110. Router 102can then perform packet forwarding using LPM database 108 and LEMdatabase 110.

In some embodiments, LPM database 108 can be a database implementedusing associative memory. For example, LPM database 108 can be databaseimplemented using TCAM. LPM database 108 can be implemented usingvarious other associative memory systems. LPM database 108 can beimplemented using various other types of specialized hardware. Router102 can store a portion of the compressed FIB 106 into LPM database 108.In some embodiments, router 102 can store forwarding entries withrouting prefixes different than /24 and /32 into LPM database 108.Router 102 can store the forwarding entries starting with the forwardingentries having routing prefixes of shortest length until there is nomore space in LPM database 108. LPM database 108 can store forwardingentries with routing prefixes having prefix lengths different than otherprefix lengths.

In some embodiments. LEM database 110 can be a hardware implementeddatabase implemented using associative memory. For example, LEM database110 can be database implemented using TCAM. LEM database 110 can beimplemented using various other associative memory systems. LEM database110 can be implemented using various other types of specializedhardware. Router 102 can store the portion of the compressed FIB 106that is not stored in LPM database 108 in LEM database 110. In otherwords, router 102 can store forwarding entries with routing prefixesequal to /24 and /32 into LEM database 110. LEM database 110 can storeforwarding entries with routing prefixes having prefix lengths of otherlengths. Moreover, the combination of LPM database 108 and LEM database110 can store the entire network (e.g., the Internet) routing tablerepresented in compressed FIB 106.

In some embodiments, router 102 can separate the forwarding entries fromcompressed FIB 106 into LPM database 108 and LEM database 110. Router102 can separate the forwarding entries from compressed FIB 106 into LPMdatabase 108 and LEM database 110 based on prefix length. For example,router 102 can program forwarding entries with routing prefixes havingprefix lengths of /24 and /32 into LEM database 110. Router 102 can thenprogram the remaining forwarding entries from compressed FIB 106 intoLPM database 108. Router 102 can program forwarding entries with routingprefixes of other lengths into LEM database 110. Router 102 can alsoprogram the remaining forwarding entries from compressed FIB 106 intoLPM database 108 based on other prefix lengths.

In some embodiments, router 102 can break down forwarding entries withrouting prefixes of prefix length /23 from compressed FIB 106 into twoforwarding entries with routing prefixes of prefix length /24 prior toseparating the forwarding entries into LPM database 108 and LEM database110. For example, router 102 can break down a forwarding entry with arouting prefix of 23.23.22.0/23 into forwarding entries with routingprefixes: 23.23.22.0/24 and 23.23.23.0/24. The two routing prefixes of23.23.22.0/24 and 23.23.23.0/24 can together be equivalent to therouting prefix 23.23.22.0/23. After breaking down the forwarding entrieswith routing prefixes of prefix length /23, router 102 can program LEMdatabase 110 using the resulting forwarding entries with routingprefixes of prefix length /24. Router 102 can break down forwardingentries with other length routing prefixes (e.g., prefix length of /2,/4, /8, /16, /48, /96, etc.) from compressed FIB 106 into two forwardingentries with routing prefixes that together are equivalent to theoriginal forwarding entry.

In some embodiments, router 102 can program forwarding entries into LPMdatabase 108 using the forwarding entries not programmed into LEMdatabase 110. Router 102 can program the forwarding entries into LPMdatabase 108 starting from the forwarding entries having the shortestrouting prefixes. Router 102 can continue to program the forwardingentries into LPM database 108 until there is no more memory to storeforwarding entries in LPM database 108.

Router 102 can determine where to forward a packet (e.g., packet 202) byperforming a lookup in either LPM database 108 or LEM database 110. Insome embodiments, router 102 can first perform a lookup in LEM database110 by matching the destination address of the packet to routingprefixes of forwarding entries in LEM database 110. If router 102 cannotmatch the destination address of the packet with routing prefixes of theforwarding entries in LEM database 110, router 102 can then perform alookup in LPM database 108. For example, router 102 can attempt to matchthe destination address of the packet with the routing prefixes of theforwarding entries in LPM database 108. If router 102 cannot match thedestination address of the packet with the routing prefixes of theforwarding entries in LPM database 108, router 102 can drop the packet.

FIG. 4 is a flowchart for a method 400 for representing a FIB includingthe routing prefixes for the network (e.g., the Internet) in one or moredatabases, according to some embodiments. Method 400 can be performed byprocessing logic that can include hardware (e.g., circuitry, dedicatedlogic, programmable logic, microcode, etc.), software (e.g.,instructions executing on a processing device), or a combinationthereof. It is to be appreciated that not all steps may be needed toperform the disclosure provided herein. Further, some of the steps maybe performed simultaneously, or in a different order than shown in FIG.4.

Method 400 shall be described with reference to FIGS. 1 and 2. However,method 400 is not limited to that embodiment.

In 402, router 102 determines that a second routing prefix of a secondforwarding entry in FIB 106 is a less specific routing prefix than afirst routing prefix in a first forwarding entry in FIB 106. In someembodiments, router 102 can perform this determination by representingFIB 106 using a trie data structure (e.g., trie data structure 300). Forexample, router 102 can determine that the second routing prefix is aless specific routing prefix than the first routing prefix if the secondrouting prefix is represented as a parent node (or parent routingprefix) of the first routing prefix in the trie data structure.

In 404, router 102 determines whether a first next hop of the firstrouting prefix of the first forwarding entry in FIB 106 is the same as asecond next hop of a second routing prefix of the second forwardingentry stored in FIB 106.

In 406, router 102 marks the first forwarding entry in FIB 106 forcompression based on the determination that the first next hop of thefirst routing prefix is the same as the second next hop of the secondrouting prefix. Router 102 can remove the first forwarding entry markedfor compression from FIB 106. Router 102 can also avoid inserting thefirst forwarding entry into LPM database 108 or LEM database 110.

In 408, router 102 can optionally generate a first sub routing prefixand a second sub routing prefix from a routing prefix in a forwardingentry based on a prefix length of the routing prefix. In someembodiments, router 102 can generate the first sub routing prefix andthe second sub routing prefix from the routing prefix in the forwardingentry based on the routing prefix having a prefix length of /23. Theresulting first sub routing prefix and the second sub routing prefix canbe of prefix length /24.

In some other embodiments, router 102 can generate the first sub routingprefix and the second sub routing prefix from the routing prefix in theforwarding entry based on the routing prefix having a prefix length of/31. The resulting first sub routing prefix and the second sub routingprefix can be of prefix length /32.

In some embodiments, router 102 can create respective forwarding entriesfor the first sub routing prefix and the second routing prefix. Therespective forwarding entries can map the first sub routing prefix andthe second routing prefix to the next hop associated with the originalforwarding entry. Router 102 can insert the respective forwardingentries into FIB 106. Router 102 can remove the original forwardingentry from FIB 106.

In 410, router 102 can optionally insert a forwarding entry from FIB 106into LEM database 110 based on the forwarding entry having a routingprefix of one or more specific lengths. For example, router 102 caninsert the forwarding entry into LEM database 110 based on the routingprefix of the forwarding entry having a prefix length of /24 or /32.

In 412, router 102 can optionally insert a forwarding entry from FIB 106into LPM database 108 based on the forwarding entry having a routingprefix having a prefix length different than one or more specificlengths from operation 410. For example, router 102 can insert theforwarding entry into LPM database 108 based on the routing prefix ofthe forwarding entry having a prefix length different than /24 or /32.

Various embodiments may be implemented, for example, using one or morewell-known computer systems, such as computer system 500 shown in FIG.5. One or more computer systems 500 may be used, for example, toimplement any of the embodiments discussed herein, as well ascombinations and sub-combinations thereof.

Computer system 500 may include one or more processors (also calledcentral processing units, or CPUs), such as a processor 504. Processor504 may be connected to a communication infrastructure or bus 506.

Computer system 500 may also include user input/output device(s) 503,such as monitors, keyboards, pointing devices, etc., which maycommunicate with communication infrastructure 506 through userinput/output interface(s) 502.

One or more of processors 504 may be a graphics processing unit (GPU).In an embodiment, a GPU may be a processor that is a specializedelectronic circuit designed to process mathematically intensiveapplications. The GPU may have a parallel structure that is efficientfor parallel processing of large blocks of data, such as mathematicallyintensive data common to computer graphics applications, images, videos,etc.

Computer system 500 may also include a main or primary memory 508, suchas random access memory (RAM). Main memory 508 may include one or morelevels of cache. Main memory 508 may have stored therein control logic(i.e., computer software) and/or data.

Computer system 500 may also include one or more secondary storagedevices or memory 510. Secondary memory 510 may include, for example, ahard disk drive 512 and/or a removable storage device or drive 514.Removable storage drive 514 may be a floppy disk drive, a magnetic tapedrive, a compact disk drive, an optical storage device, tape backupdevice, and/or any other storage device/drive.

Removable storage drive 514 may interact with a removable storage unit518. Removable storage unit 518 may include a computer usable orreadable storage device having stored thereon computer software (controllogic) and/or data. Removable storage unit 518 may be a floppy disk,magnetic tape, compact disk, DVD, optical storage disk, and/any othercomputer data storage device. Removable storage drive 514 may read fromand/or write to removable storage unit 518.

Secondary memory 510 may include other means, devices, components,instrumentalities or other approaches for allowing computer programsand/or other instructions and/or data to be accessed by computer system500. Such means, devices, components, instrumentalities or otherapproaches may include, for example, a removable storage unit 522 and aninterface 520. Examples of the removable storage unit 522 and theinterface 520 may include a program cartridge and cartridge interface(such as that found in video game devices), a removable memory chip(such as an EPROM or PROM) and associated socket, a memory stick and USBport, a memory card and associated memory card slot, and/or any otherremovable storage unit and associated interface.

Computer system 500 may further include a communication or networkinterface 524. Communication interface 524 may enable computer system500 to communicate and interact with any combination of externaldevices, external networks, external entities, etc. (individually andcollectively referenced by reference number 528). For example,communication interface 524 may allow computer system 500 to communicatewith external or remote devices 528 over communications path 526, whichmay be wired and/or wireless (or a combination thereof), and which mayinclude any combination of LANs, WANs, the Internet, etc. Control logicand/or data may be transmitted to and from computer system 500 viacommunication path 526.

Computer system 500 may also be any of a personal digital assistant(PDA), desktop workstation, laptop or notebook computer, netbook,tablet, smart phone, smart watch or other wearable, appliance, part ofthe Internet-of-Things, and/or embedded system, to name a fewnon-limiting examples, or any combination thereof.

Computer system 500 may be a client or server, accessing or hosting anyapplications and/or data through any delivery paradigm, including butnot limited to remote or distributed cloud computing solutions; local oron-premises software (“on-premise” cloud-based solutions); “as aservice” models (e.g., content as a service (CaaS), digital content as aservice (DCaaS), software as a service (SaaS), managed software as aservice (MSaaS), platform as a service (PaaS), desktop as a service(DaaS), framework as a service (FaaS), backend as a service (BaaS),mobile backend as a service (MBaaS), infrastructure as a service (IaaS),etc.); and/or a hybrid model including any combination of the foregoingexamples or other services or delivery paradigms.

Any applicable data structures, file formats, and schemas in computersystem 500 may be derived from standards including but not limited toJavaScript Object Notation (JSON), Extensible Markup Language (XML), YetAnother Markup Language (YAML), Extensible Hypertext Markup Language(XHTML), Wireless Markup Language (WML), MessagePack, XML User InterfaceLanguage (XUL), or any other functionally similar representations aloneor in combination. Alternatively, proprietary data structures, formatsor schemas may be used, either exclusively or in combination with knownor open standards.

In some embodiments, a tangible, non-transitory apparatus or article ofmanufacture comprising a tangible, non-transitory computer useable orreadable medium having control logic (software) stored thereon may alsobe referred to herein as a computer program product or program storagedevice. This includes, but is not limited to, computer system 500, mainmemory 508, secondary memory 510, and removable storage units 518 and522, as well as tangible articles of manufacture embodying anycombination of the foregoing. Such control logic, when executed by oneor more data processing devices (such as computer system 500), may causesuch data processing devices to operate as described herein.

Based on the teachings included in this disclosure, it will be apparentto persons skilled in the relevant art(s) how to make and useembodiments of this disclosure using data processing devices, computersystems and/or computer architectures other than that shown in FIG. 5.In particular, embodiments can operate with software, hardware, and/oroperating system implementations other than those described herein.

It is to be appreciated that the Detailed Description section, and notany other section, is intended to be used to interpret the claims. Othersections can set forth one or more but not all exemplary embodiments ascontemplated by the inventor(s), and thus, are not intended to limitthis disclosure or the appended claims in any way.

While this disclosure describes exemplary embodiments for exemplaryfields and applications, it should be understood that the disclosure isnot limited thereto. Other embodiments and modifications thereto arepossible, and are within the scope and spirit of this disclosure. Forexample, and without limiting the generality of this paragraph,embodiments are not limited to the software, hardware, firmware, and/orentities illustrated in the figures and/or described herein. Further,embodiments (whether or not explicitly described herein) havesignificant utility to fields and applications beyond the examplesdescribed herein.

Embodiments have been described herein with the aid of functionalbuilding blocks illustrating the implementation of specified functionsand relationships thereof. The boundaries of these functional buildingblocks have been arbitrarily defined herein for the convenience of thedescription. Alternate boundaries can be defined as long as thespecified functions and relationships (or equivalents thereof) areappropriately performed.

Also, alternative embodiments can perform functional blocks, steps,operations, methods, etc. using orderings different than those describedherein.

References herein to “one embodiment,” “san embodiment,” “an exampleembodiment,” or similar phrases, indicate that the embodiment describedcan include a particular feature, structure, or characteristic, butevery embodiment can not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it would be within the knowledge of persons skilled in therelevant art(s) to incorporate such feature, structure, orcharacteristic into other embodiments whether or not explicitlymentioned or described herein. Additionally, some embodiments can bedescribed using the expression “coupled” and “connected” along withtheir derivatives. These terms are not necessarily intended as synonymsfor each other. For example, some embodiments can be described using theterms “connected” and/or “coupled” to indicate that two or more elementsare in direct physical or electrical contact with each other. The term“coupled,” however, can also mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other.

The breadth and scope of this disclosure should not be limited by any ofthe above-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. A computer implemented method for representing aforwarding information base (FIB) in a database, comprising:determining, by at least one processor, that a first routing prefix of afirst forwarding entry in the FIB is a less specific routing prefix thana second routing prefix in a second forwarding entry in the FIB;determining, by the at least one processor, a first next hop of thefirst routing prefix is equal to a second next hop of the second routingprefix; removing, by the at least one processor, the second forwardingentry from the FIB based on the determination that the first next hop ofthe first routing prefix is equal to the second next hop of the secondrouting prefix; and inserting, by the at least one processor, the firstforwarding entry into a longest exact match (LEM) database or a longestprefix match (LPM) database based on a prefix length of the firstrouting prefix of the first forwarding entry.
 2. The method of claim 1,wherein the first next hop comprises a next hop address and an outgoinginterface.
 3. The method of claim 1, wherein the inserting comprisesinserting the first forwarding entry into the LPM database based on theprefix length of the first routing prefix of the first forwarding entrybeing different than 24 bits or 32 bits.
 4. The method of claim 1,wherein the inserting comprises inserting the first forwarding entryinto the LEM database based on the prefix length of the first routingprefix of the first forwarding entry being 24 bits or 32 bits.
 5. Themethod of claim 1, wherein each of the LEM and LPM databases compriseternary content-addressable memory (TCAM).
 6. The method of claim 1,further comprising: generating a first sub routing prefix and a secondsub routing prefix from a third routing prefix of a third forwardingentry in the FIB based on a prefix length of the third routing prefixbeing 23 bits.
 7. The method of claim 6, further comprising: insertingthe first sub routing prefix and the second sub routing prefix into theLEM database.
 8. A system, comprising: a memory; and at least oneprocessor coupled to the memory and configured to: determine that afirst routing prefix of a first forwarding entry in a forwardinginformation base (FIB) is a less specific routing prefix than a secondrouting prefix in a second forwarding entry in the FIB; determine afirst next hop of the first routing prefix is equal to a second next hopof the second routing prefix; remove the second forwarding entry fromthe FIB based on the determination that the first next hop of the firstrouting prefix is equal to the second next hop of the second routingprefix; and insert the first forwarding entry into a database based on aprefix length of the first routing prefix of the first forwarding entry.9. The system of claim 8, wherein the first next hop comprises a nexthop address and an outgoing interface.
 10. The system of claim 8,wherein to insert the first forwarding entry, the at least one processoris configured to insert the first forwarding entry into the databasebased on the prefix length of the first routing prefix of the firstforwarding entry being different than 24 bits or 32 bits, wherein thedatabase comprises a longest prefix match (LPM) database.
 11. The systemof claim 8, wherein to insert the first forwarding entry, the at leastone processor is configured to insert the first forwarding entry intothe database based on the prefix length of the first routing prefix ofthe first forwarding entry being 24 bits or 32 bits, wherein thedatabase comprises a longest exact match (LEM) database.
 12. The systemof claim 8, wherein the database comprises ternary content-addressablememory (TCAM).
 13. The system of claim 8, wherein the at least oneprocessor is further configured to generate a first sub routing prefixand a second sub routing prefix from a third routing prefix of a thirdforwarding entry in the FIB based on a prefix length of the thirdrouting prefix being 23 bits.
 14. The system of claim 13, wherein the atleast one processor is further configured to insert the first subrouting prefix and the second sub routing prefix into the database. 15.A non-transitory computer-readable device having instructions storedthereon that, when executed by at least one computing device, causes theat least one computing device to perform operations comprising:determining that a first routing prefix of a first forwarding entry in aforwarding information base (FIB) is a less specific routing prefix thana second routing prefix in a second forwarding entry in the FIB;determining a first next hop of the first routing prefix is equal to asecond next hop of the second routing prefix; removing the secondforwarding entry from the FIB based on the determination that the firstnext hop of the first routing prefix is equal to the second next hop ofthe second routing prefix; and inserting the first forwarding entry intoan exact match database based on a prefix length of the first routingprefix of the first forwarding entry being 24 bits or 32 bits.
 16. Thenon-transitory computer-readable device of claim 15, wherein theinserting comprises inserting a third forwarding entry into a longestprefix match (LPM) database based on a prefix length of a third routingprefix of the third forwarding entry being different than 24 bits or 32bits.
 17. The non-transitory computer-readable device of claim 15,wherein the FIB is organized using a trie data structure.
 18. Thenon-transitory computer-readable device of claim 16, wherein each of theexact match and LPM databases comprise ternary content-addressablememory (TCAM).
 19. The non-transitory computer-readable device of claim15, wherein the operations further comprise generating a first subrouting prefix and a second sub routing prefix from a third routingprefix of a third forwarding entry in the FIB based on a prefix lengthof the third routing prefix being 23 bits.
 20. The non-transitorycomputer-readable device of claim 19, wherein the operations furthercomprise inserting the first sub routing prefix and the second subrouting prefix into the exact match database.